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The two alluvial aquifer systems present within the Edna permit area aze the Oak Creek <br />and Trout Creek alluvial aquifers. Both of the alluvial aquifers are in direct hydraulic <br />communication with each associated stream. <br />Baseline water quality data from the Trout Creek alluvial aquifer indicates that the quality <br />of this water is suitable for agricultural purposes. The water is moderately low in TDS <br />levels (less than 350 mg/1) and exhibits a low SAR. The water quality of the Oak Creek <br />alluvial aquifer is generally lower than that found in the Trout Creek alluvium (TDS <br />levels ranging from 400 to 1700 mg/1). This may be attributable to the levels of <br />disturbance and activities already present along the Oak Creek valley. These activities <br />include the presence of roads and railroads situated atop the alluvium and disturbance <br />from past mining activities. <br />The Trout Creek alluvial aquifer roughly pazallels the western boundary of the permit <br />area. Currently, the Trout Creek alluvial aquifer is monitored by 5 wells. Depth-to-water <br />and water quality trends above, adjacent to and below the mine site are observed. A <br />degradation of the alluvial water quality has occurred, and will continue to occur, in the <br />alluvium adjacent to portions of the Edna site which have been mined. An alluvial ground <br />water point of compliance has been established in the Trout Creek alluvial aquifer. At the <br />time of this Permit Renewal 5, ground water is in compliance with applicable laws and <br />regulations with regard to the point of compliance. <br />The re-saturation of backfilled pits has been expressed as spoil aquifers. When the <br />elevation head of the aquifer which has developed exceeds the topographic low point <br />along the buried highwall, water is dischazged at the surface in the form of springs. <br />Numerous springs and seeps have been identified along the areas mined adjacent to Trout <br />Creek. These springs and seeps dischazge water which is high in TDS and sulfates to the <br />alluvial aquifers, as well as directly to Trout Creek. <br />Surface Water <br />The permit area lies in the upper Yampa River basin. This basin is drained by several <br />ephemeral streams which flow into Trout Creek and Oak Creek. Trout Creek and Oak <br />Creek are both perennial streams which flow in a northeasterly direction toward the <br />Yampa River. A ridge on the east side of the permit area divides surface runoff into the <br />two drainages. Approximately 140 acres of the permit area aze located in the Oak Creek <br />drainage, the rest in the Trout Creek Drainage. <br />Both Trout Creek and Oak Creek aze incised into bedrock, with Trout Creek draining <br />approximately 54 square miles above the northern limit of the mine, while Oak Creek <br />drains approximately 32 squaze miles. Runoff events in both these streams are dominated <br />by snowmelt. Peak spring runoff occurs slightly later in Trout Creek than in Oak Creek <br />because the headwaters of the former are located at a much higher elevation. <br />Mining operations facilities aze not subject to significant impact by large flood events <br />from these streams. With the exception of a water (extraction) pumping site and creek <br />monitoring stations, the Trout Creek floodplain is well below past and current mining <br />C-1980-001 Permit Renewal 5 Findings Page 9 of 33 Pages <br />